The human body requires a controlled temperature for normal physiological processes to work properly. Because of this need, the body is endowed with a complex array of systems for regulating thermal homeostasis. The heat of metabolism is substantial and must be exhausted to the surrounding environment to prevent overheating. However if the heat loss is too great, hypothermia may result. For this and other reasons the body is equipped to maintain thermal equilibrium for a broad range of environmental conditions.
Many of the body's mechanisms for achieving thermal equilibrium are automatic (e.g., sweating, shivering, and vasodilatation). These are beyond the conscious control of the individual and usually suffice to keep the core temperature at a constant level. The body also seeks to maintain thermal equilibrium through conscious behavior: altering posture, clothing, or changing indoor temperatures. Thus, the subjective feeling of being hot or cold assists the body in maintaining thermal homeostasis, and these feelings are attuned to the person's surrounding environment.
Normally extreme heat or cold are required to overcome the body's ability to thermoregulate itself. However, certain drugs and anesthetic agents can reduce the body's ability to respond to thermal challenge. This factor makes surgical patients particularly vulnerable to hypothermia, and a variety of devices have been developed to address this situation. For surgical patients, it is important to make up for the loss of automatic thermoregulatory mechanisms. While these patients are anesthetized and unconscious, subjective feelings of discomfort are typically not an issue in their treatment.
However if the patient is conscious, poor thermoregulation can result in acute feelings of discomfort. Even if the patient is clinically normothermic it is still likely that they will experience subjective sensations of “feeling cold”. Indeed, this is the primary complaint of many post-surgical patients. Thus, for these patients, preventing or treating hypothermia alone is not sufficient; one must also meet the needs of thermal comfort.
“Thermal comfort” for a person is defined by P. O. Fanger as “that condition of mind which expresses satisfaction with the thermal environment”. Fanger, Thermal Comfort: Analysis and Applications in Environmental Engineering, Danish Technical Press, Copenhagen, 1970. Now, it is increasingly apparent that making patients thermally comfortable is a desirable clinical objective. Aside from humanitarian concerns, there are many good reasons to provide for the thermal comfort of a patient:
Anxiolysis—the reduction of anxiety has been shown to have beneficial effects in patient outcomes
Nursing time—Nurses need not spend their time responding to patients' request for more or different thermal comfort interventions.
Some clinics address their patients' thermal comfort needs by raising the room temperature. This is expensive and unnecessary when patients can control their own microenvironment.
Patient satisfaction is a growing concern among competing hospitals. Lack of thermal comfort is a frequent complaint among patients, and results in poor patient ratings.
Therefore, the provision of means to enable a patient to selectively control the thermal characteristics of his or her own personal microenvironment in a medical setting should produce the following unexpected benefits: 1.) reduced blood pressure and easier IV access; 2.) reduced pain sensation; 3.) normalizing of the patient's perception of time slowing; 4.) reduced anxiety and reduced need for medication. These and other objectives are realized when a patient is maintained in a state of thermal comfort.